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Collaborative Research: Dissolved organic phosphorus controls on marine nitrogen fixation and export production

合作研究：溶解有机磷对海洋固氮和出口生产的控制

基本信息

批准号：
1829916
负责人：
Robert Letscher
金额：
$ 11.5万
依托单位：
University of New Hampshire
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2018
资助国家：
美国
起止时间：
2018-09-01 至 2022-08-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1829916&HistoricalAwards=false
关键词：
Collaborative Research Dissolved organic phosphorus

项目摘要

Phytoplankton play an important role in the Earth's elemental cycles of carbon and nitrogen. In addition to sunlight, phytoplankton living in the surface waters of the oceans require the elements nitrogen and phosphorus for growth. Much of these nutrients are supplied in their inorganic forms from mixing of deep waters towards the surface during the winter months when vertical stability of the water column breaks down. However much of the low latitude oceans, 45degS45degN, suffer from limited nutrient input to sunlit surface waters due to strong thermal stratification (vertical stability) of the upper water column. As a consequence, tropical and subtropical phytoplankton have devised alternative ways of acquiring nitrogen and phosphorus. Marine nitrogen fixation is a process by which specialized microbes utilize the abundant nitrogen gas from the atmosphere to convert elemental nitrogen into the bioavailable form ammonia. These nitrogen fixing phytoplankton and many others also use organic forms of phosphorus in the low latitude ocean where inorganic nutrients are often scarce. This project will significantly increase the number of dissolved organic nitrogen and dissolved organic phosphorus concentration measurements, especially from the currently under-sampled Pacific and Indian Oceans. Changes in the concentration of organic nutrients across the surface ocean will be used to infer rates of organic nutrient use by phytoplankton in numerical models. Specifically, the role for the biological uptake of dissolved organic phosphorus to stimulate the processes of marine nitrogen fixation and photosynthesis in the low latitude ocean will be quantified from the combined data and model output. The project will train one graduate student and several undergraduate students in both laboratory chemical analysis techniques and numerical simulation of ocean biological and chemical processes. New scientific knowledge will be shared with the public via a social media campaign and will inform the development of the next generation of global climate models. The marine biogeochemical modeling community has identified the lack of dissolved organic nitrogen (DON) and especially dissolved organic phosphorus (DOP) concentration measurements from the upper 300 m of the global ocean as crucial gaps in our ability to accurately model export production and N2 fixation rates in the subtropics. The proposed work will significantly increase global data coverage of marine DON and DOP concentration measurements, in particular from under-sampled ocean regions in the Indian Ocean, western, central, and eastern tropical South Pacific, Gulf of Alaska, eastern subtropical and subpolar South Pacific, Southern Ocean, subtropical North Atlantic, and tropical South Atlantic Ocean basins. These new measurements will be assimilated in state-of-the-art biogeochemical models to constrain the relative cycling rates of DOP and DON and to quantify the role of preferential DOP consumption as a P source supporting export production and N2 fixation in the low latitude ocean. Model output will solve for the regionally-resolved fraction of new production that accumulates as DON and DOP, autotrophic DOP uptake rates, as well as the remineralization rates for DON and DOP. The model output will also include the first regionally variable rate estimates of euphotic zone DOP consumption sustaining export production and N2 fixation to be constrained by observations from the Pacific and Indian Oceans. Thus, the new concentration measurements and diagnostic modeling will allow us to evaluate the quantitative role for regional variability in DOP consumption and recycling that supports export production and N2 fixation in the low latitude ocean.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

浮游植物在地球的碳和氮元素循环中起着重要作用。除了阳光，生活在海洋表面沃茨的浮游植物需要氮和磷元素来生长。这些营养物大部分是以无机形式提供的，在冬季，当水柱的垂直稳定性下降时，深层沃茨向表面混合。然而，许多低纬度海洋，45 degS45 degN，遭受有限的营养输入到阳光照射的表面沃茨由于强烈的热分层（垂直稳定性）的上层水柱。因此，热带和亚热带的浮游植物已经设计出获取氮和磷的替代方式。海洋固氮是一种特殊微生物利用大气中丰富的氮气将元素氮转化为生物可利用的氨的过程。这些固氮浮游植物和许多其他浮游植物也使用低纬度海洋中无机营养物通常稀缺的有机形式的磷。该项目将大大增加溶解有机氮和溶解有机磷浓度测量的数量，特别是从目前采样不足的太平洋和印度洋。整个海洋表层有机营养物浓度的变化将被用来推断数值模型中浮游植物对有机营养物的利用率。具体而言，生物吸收溶解有机磷以刺激低纬度海洋的海洋固氮和光合作用过程的作用将从合并的数据和模式输出中量化。该项目将在实验室化学分析技术和海洋生物和化学过程的数值模拟方面培训一名研究生和几名本科生。新的科学知识将通过社交媒体活动与公众分享，并将为下一代全球气候模型的开发提供信息。海洋生物地球化学建模界已经发现，缺乏全球海洋上层300 m的溶解有机氮（DON），尤其是溶解有机磷（DOP）浓度测量值，是我们准确建模出口生产和N2固定率能力的关键差距。亚热带地区。拟议的工作将显著增加海洋DON和DOP浓度测量的全球数据覆盖范围，特别是来自印度洋，热带南太平洋西部，中部和东部，阿拉斯加湾，东亚热带和亚极地南太平洋，南大洋，亚热带北大西洋和热带南大西洋盆地的采样不足的海洋区域。这些新的测量结果将被同化在国家的最先进的海洋地球化学模型，以限制DOP和DON的相对循环速率，并量化的作用，优先DOP消费作为一个P源，支持出口生产和N2固定在低纬度海洋。模型输出将解决新生产的区域分辨分数，积累为DON和DOP，自养DOP吸收率，以及DON和DOP的再矿化率。模型输出还将包括真光层DOP消费的第一次区域可变速率估计，以维持出口生产和N2固定，这将受到太平洋和印度洋观测的限制。因此，新的浓度测量和诊断模型将使我们能够评估DOP消耗和回收的区域变化的定量作用，支持低纬度海洋的出口生产和N2固定。该奖项反映了NSF的法定使命，并被认为是值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估的支持。